1. Field of the Invention
The present invention relates to a method of fabricating an active matrix-type light-emitting device having a light-emitting element on a substrate, and to a light-emitting device. The light-emitting element stands for an element of a structure having an anode, a cathode and an organic compound layer containing a light-emitting organic material (hereinafter referred to as organic material) that produces EL (electroluminescence) sandwiched therebetween. The light-emitting element referred to here is also called OLED (organic light-emitting device). In this specification, further, a light-emitting panel having a light-emitting element sealed between a substrate and a covering member, and a light-emitting module having an IC mounted on the light-emitting panel, are generally referred to as light-emitting devices. The invention is further concerned with electric appliances using the above light-emitting device on the display unit. The EL (electroluminescent) devices referred to in this specification include triplet-based light emission devices and/or singlet-based light emission devices, for example.
2. Prior Art
The light-emitting element is highly visible since it emits light by itself, is best suited for decreasing the thickness since it does not use backlight needed by the liquid crystal display devices (LCDs), and imposes no limitation on the viewing angle. In recent years, therefore, the light-emitting device using the light-emitting element is drawing attention to substitute for the CRTs and LCDs.
The light-emitting element includes a layer containing an organic material that produces EL (electroluminescence: luminescence which is produced upon the application of a electric field), an anode and a cathode. The luminescence produced by the organic material can be classified into emission of light (fluorescence) of when the singlet excitation state returns back to the ground state and emission of light (phosphorescence) of when the triplet excitation state returns back to the ground state. The light-emitting device of the present invention may use the light-emitting element containing either organic material.
In this specification, the layers provided between the anode and the cathode are all defined as organic compound layers. Concretely speaking, the organic compound layers include a light-emitting layer, a positive hole injection layer, an electron injection layer, a positive hole transporting layer and an electron transporting layer. Basically, the light-emitting element has a structure in which the anode/light-emitting layer/cathode are laminated in this order. In addition to this structure, the light-emitting element may often have a structure in which the anode/positive hole injection layer/light-emitting layer/cathode are laminated in this order or the anode/positive hole injection layer/light-emitting layer/electron transporting layer/cathode are laminated in this order.
In forming the light-emitting element, the layer of the organic compound is formed by the vaporization method, printing method, ink-jet method or spin-coating method.
Among them, the vaporization method capable of separately applying the organic compound by using a metal mask or the like mask, is one of the film-forming methods frequently used for forming a film of a low-molecular organic material. In forming the active matrix-type light-emitting element, however, this method arouses a problem in that the pixels are damaged when the metal mask comes in contact with the pixels in forming the film of the organic compound, since the light-emitting elements are formed after the TFTs are formed.
According to the conventional method of fabricating the light-emitting element as taught in Japanese Patent Laid-Open No. 339968/1999, however, the passivation film is formed after the pixel electrode is formed, and the organic compound layer and the opposing electrode are formed after the passivation film is removed from the pixel electrode portion. Therefore, there has been formed a structure for protection with the passivation film so that the metal mask will not come in contact with the pixels. In this specification, the passivation film formed except on the pixel electrodes is called bank.
By forming the bank prior to forming the layer of the organic compound and the opposing electrodes as described above, it is allowed to prevent the metal mask from coming into contact with the pixels.
In fabricating the light-emitting element, the bank comprising an insulating material is formed to surround the pixels after the pixel electrode is formed for each of the pixels.
The bank works not only to protect the wiring but also to protect the pixel electrodes of the pixels, the organic compound layer and the opposing electrodes from being damaged when they are touched by the metal mask in forming the organic compound layer and the opposing electrodes by vaporization on the pixel electrodes of the pixels by using the metal mask, and to prevent the electrodes from being short-circuited to the wiring at the time when the opposing electrodes are formed.
However, formation of the bank requires another piece of mask for patterning.